Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified						12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Commitments to Extend Credit [Member]	Dec. 31, 2011 Commitments to Extend Credit [Member]	Dec. 31, 2012 Letters of Credit [Member]	Dec. 31, 2011 Letters of Credit [Member]	Dec. 31, 2012 Letters of Credit [Member] Minimum [Member]	Dec. 31, 2012 Letters of Credit [Member] Maximum [Member]	Dec. 31, 2012 Performance Guarantees Under Interest Rate Swap Contracts Entered Into Between Our Borrowing Customers and Third Parties [Member]	Dec. 31, 2011 Performance Guarantees Under Interest Rate Swap Contracts Entered Into Between Our Borrowing Customers and Third Parties [Member]
Off-balance sheet risks [Line Items]
Off-balance sheet risks, amount, liability		$ 334,772	$ 300,572	$ 5,281	$ 5,087			$ 1,796	$ 416
Off balance sheet risks maturity period						1 month	48 months
Minimum future rental commitments under noncancellable operating leases [Abstract]
2013	279,000
2014	292,000
2015	287,000
2016	122,000
2017	$ 14,000